Omega-3 fatty acid

N−3 fatty acids (popularly referred to as ω−3 fatty acids or omega-3 fatty acids) are essential unsaturated fatty acids with a double bond (C=C) starting after the third carbon atom from the end of the carbon chain.

Essential fatty acids are molecules that cannot be synthesized by the human body but are vital for normal metabolism. One of the two families of these essential fatty acids is the omega-3 fatty acids. The carbon chain has two ends -- the acid (COOH) end and the methyl (CH3) end. The location of the first double bond is counted from the methyl end, which is also known as the omega (ω) end or the n end.

Nutritionally important n−3 fatty acids include α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), all of which are polyunsaturated. Common sources of n–3 fatty acids include fish oils and some plant oils such as flaxseed oil and algal oil, though the latter's bioavailability is disputed in the Paleolithic community.

Mammals cannot synthesize n−3 fatty acids, but have a limited ability to form the "long-chain" n−3 fatty acids EPA (20-carbon atoms) and DHA (22-carbon atoms) from the "short-chain" eighteen-carbon n−3 fatty acid ALA.